linux-kernel - Re: [PATCH] bluetooth: hci_h5: avoid unused variable warnings

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Message-Id: <8F488B14-4425-44A4-9E6D-58513FED5256@holtmann.org>
Date:   Tue, 14 Aug 2018 09:02:46 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Jeremy Cline <jeremy@...ine.org>,
        Kees Cook <keescook@...omium.org>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bluetooth: hci_h5: avoid unused variable warnings

Hi Arnd,

> When CONFIG_BT_HCIUART_RTL is disabled, the hci_h5 driver produces a build
> warning because of an incorrect set of #ifdef guards:
> 
> drivers/bluetooth/hci_h5.c:920:22: error: 'rtl_vnd' defined but not used [-Werror=unused-variable]
> 
> Replacing the #ifdef with an IS_ENABLED() check shuts up the error
> and simplifies the logic.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> drivers/bluetooth/hci_h5.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_h5.c b/drivers/bluetooth/hci_h5.c
> index 8eede1197cd2..b10e64ba0ff4 100644
> --- a/drivers/bluetooth/hci_h5.c
> +++ b/drivers/bluetooth/hci_h5.c
> @@ -841,7 +841,6 @@ static void h5_serdev_remove(struct serdev_device *serdev)
> 	hci_uart_unregister_device(&h5->serdev_hu);
> }
> 
> -#ifdef CONFIG_BT_HCIUART_RTL
> static int h5_btrtl_setup(struct h5 *h5)
> {
> 	struct btrtl_device_info *btrtl_dev;
> @@ -923,24 +922,21 @@ static struct h5_vnd rtl_vnd = {
> 	.close		= h5_btrtl_close,
> 	.acpi_gpio_map	= acpi_btrtl_gpios,
> };
> -#endif
> 
> -#ifdef CONFIG_ACPI
> static const struct acpi_device_id h5_acpi_match[] = {
> -#ifdef CONFIG_BT_HCIUART_RTL
> 	{ "OBDA8723", (kernel_ulong_t)&rtl_vnd },
> -#endif
> 	{ },
> };
> MODULE_DEVICE_TABLE(acpi, h5_acpi_match);
> -#endif
> 
> static struct serdev_device_driver h5_serdev_driver = {
> 	.probe = h5_serdev_probe,
> 	.remove = h5_serdev_remove,
> 	.driver = {
> 		.name = "hci_uart_h5",
> -		.acpi_match_table = ACPI_PTR(h5_acpi_match),
> +		.acpi_match_table = (IS_ENABLED(CONFIG_BT_HCIUART_RTL) &&
> +				     IS_ENABLED(CONFIG_ACPI)) ?
> +					h5_acpi_match : 0,
> 	},

I do not like this construct at all. It will also blow up once we have a second vendor with H:5 support. We need to find another way to solve this.

Regards

Marcel